Fuel pump



- Oct. 7, 1941. J, HOLLOWAY .ET AL 2,258,055

FUEL PUMP Filed April 29, 1938 zai INVENTORS ATTOY.

Patented Oct. 7, 1941 FUEL PUMP John H.. Holloway, Green .Bay, and MoyesJ. Murphy, Milwaukee; Wis., assignors to Murphy Diesel Company,acorporation of Delaware Application April 29, 1938, Serial No. 204,974f I *The'invention relates to fuel pumps.

The object of the "invention is to provide improvements in the cut offconstruction of that type of fuel pump having a constant stroke but avariable cut off which is produced by a groove or scroll on the plungerregistering with a relief port.

Heretofore the cut off scroll on the plunger has been of relativelylarge volume, and in some pumps having a vertically disposed plunger anda discharge valve at the lower end of the pump barrel it hasbeen'necessary to use two ports in order to properly fill the pump andfree it of en trained air. The object of the present invention is toprovid a cut off groove or scroll on the plunger of small width anddepth so as to keep the volume of the pump chamber a minimum and justsufficient to handle the flow. Furthermore; the improved cut off grooveacts to vent air from the pump barrel during the outward stroke of theplunger andalso makes the pump self cleaning. Furthermore, the cut offof this invention acts to quickly reduce the pressure at the end of theeffective stroke of the plunger. Also because of the small area of thegroove there is a minimum of leakage and side thrust against theplunger. I 1

A further object of theinvention is to provide aninclined cut off grooveon the plunger, the projection of whose inclined portion may 'be withinthe width of the relief port, so that the pump may be set to an idlingposition. j

, A'further object of the invention is to provide a cut off relief onthe plunger which is cheap and easy to make and easy to measure and hold-end of its stroke said port I! is uncovered so.

er, so that the pressures on the same may be bal- 3 Claims. (01. 1031-41) taken at substantially right angles to thr" if F 1; V Fig. 3 is aviewsimilar to Fig.2 showing the plunger in an intermediate position;

I Fig. .4 is a detailed sectional View similar to, Fig. 2 showingcertain modifications;

Fig. 5 is a detailed sectional view taken on the line 5-5 of Fig. 4';

Fig. 6. is a detailed sectional view similar Fig. 5 showing certainmodifications;

Fig. 7 is a'detailed sectional view similar to Fig. 5 showing certainmodifications.

Referring to the drawing, we have shown a pump, including a casing 4, abarrel 5 mounted in said casing, .a valve seat member 6 mounted in thereduced end of said casing and clamped thereto by a sleeve nut I whichalso clamps a flanged nozzle member 8 against said member 6.-

The nozzle member has the spray orifices 9. and

thestepped bores lll, II, and I2 leading to said A ball valve I3 isnormally held against its seat in the member 6 at the end of thedischarge passage l41therein by means of a grooved pin 15 andfla" Springl6 holding said pin against. said valve.,

The barrel forms .an inlet and a relief port and is controlled by aplunger l8 working in the barrel 5, it being noted that when saidplunger is at th inward that fuel may flow freely into the barrel, itbeing noted that a partial vacuum may exist in the pump chamber undersome conditions before th port I1 is uncovered- As previously noted thepump is of the type having a constant stroke and variable cut off, thecut off being controlled by a scroll or relief on the plungercooperating with a relief port. The plunger I8 has a shallow cut offgroove l9 formed therein by grinding or milling and having straight endportions 20 and 2| and a spirally inclined portion 22 connecting saidend portions. It will be noted from Fig. 2 that the pitch of the portion22 is such that the displacement of the edge 23 of the end portion 20 ofthe groove from the edge 24 of the end portion 2| of said groove is lessthan the width of the port l1, so that when the plunger is in its idlingposition as shown in full in Fig. 2, some portion of the groove Will atall times overlap th port I! during the entire stroke of the plunger, sothat fuel taken into the barrel will be by-passed back into the port l1during the entire stroke of the plunger. If now the plunger l8 and thbarrel 5 be ro- 5 is provided a port l'liwhich i

